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What is a passive radon system?

Passive radon systems or “radon-ready” systems—as they should be called—are pre-plumbed radon systems for a building. They do not function unless there is a radon fan added to them*. This is why it is my personal mission to remove the term “passive” from the nomenclature. It implies that the system works as is. If you have high radon levels, you’re gonna need a fan no matter what. See this new home my good friend built. He was under the impression that he had a radon system and almost didn’t test! Good thing he knew me. We tested his passive radon system and he had a whopping 11+ pCi/L, nearly three times the EPA action level! He could’ve lived decades in that home thinking he was safe.

Always perform a radon test on a passive home. This is why EPA recommended testing is important and can save your life. You don’t test a home once; you test at minimum every five years.

Why should you build a radon-ready home?

There are many benefits to building radon ready. In my opinion, the biggest benefit is: no loud, ugly radon fan on the side of your house. Yes, we know they’re loud, we know they’re ugly, but they’re better than stage IV lung cancer.

In Zone 1, high-risk states like Colorado, Iowa, or North Dakota, your chances of having dangerous radon levels are higher than having low levels. So if you’re a gambler, you’re betting against the house: literally. Even if you don’t have high radon levels, many homeowners choose to add a low-wattage fan to the system for the benefit of increased airflow under the slab. A dry slab is good for the home’s foundation and it can eliminate musty basement smells.

Other benefits of radon-ready homes are: more energy-efficient radon fans can be installed since you have perfect PFE; smaller fans are quieter fans; fan location is often in garages or attics away from occupants–again quieter; increased home value from having a radon system; and again, radon-ready systems are much more cosmetically appealing than post-construction radon systems.

Passive Radon-ready systems are the future of homebuilding. Don’t get left behind, ask your builder or realtor about radon-ready homes today! PDS offers free system designs at

*Passive radon systems can function in very specific weather conditions due to the stack effect. In North America, these weather conditions do not exist 12 months out of the year, which is why I believe the term is dangerous. If you insist on trying to use your system passively, I cannot recommend a continuous radon monitor more. Watch your radon levels fluctuate with weather patterns and see for yourself.  Passive radon systems include those called out in IRC Appendix F, ANSI/AARST RRNC 2020 and AARST-ANSI CC-1000-2018

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How to choose an energy efficient radon fan

Radon fans are already some of the most energy-efficient air movers in the marketplace.  However, a radon fan runs constantly, 24/7/365. Even the most efficient motors are going to use a lot of energy over their lifetime, so it’s in your best interest to choose an energy-efficient radon fan.

The first and most important way to get an energy efficient radon fan is to have it sized properly.  If you read my post on CFM and PFE, you’ll know that the marketplace drives radon pros to “poke and hope” in order to keep upfront costs low.  “Poking and hoping” may fix a radon problem, but it’s often going to do it with an oversized radon fan.  We’re talking 100+ watts versus 20-60.  Over the lifespan of the fan (5~15 years) that can mean hundreds of dollars in energy usage.

The next thing that an oversized radon fan can do is exhaust conditioned air from the home.  That’s air you paid for!! Radon fans are going to pull from the path of least resistance, and sometimes that means pulling from a tear in your crawl space barrier; or a hairline crack in a slab; or an expansion joint; or a poorly sealed sump; and so on, and so on.  When a large radon fan is moving 100+ cubic feet of air per minute and half of that is coming from inside your home, what do you think that does to your energy bill?  Your HVAC system has to replace that air and condition it to hospitable temperatures.  This is where the real energy costs come into play.

Case studies from leading radon professionals and educators show that merely sealing hairline cracks in a foundation on an average-sized single family home can save over $1,000 over the life of the radon fan.  If you choose a licensed radon mitigator that performs proper PFE testing and radon fan sizing you can’t go wrong.  The upfront cost of using an educated pro will be made up 10X over with the efficiency in your system.

Leading fan manufacturer, Fantech, has also introduced EC motors to the radon marketplace.  EC stands for electrically-communicated.  These motors operate more similarly to DC motors than AC.  They have built-in speed controls and run about 20% more efficiently than AC motors with similar fan curves.  With the speed control, you can also “dial in” the fan to exactly what your home needs.  A radon professional in Minnesota recently used an EC fan to depressurize a home using less than 5 watts of electricity!  EC radon fans can be twice the price of AC fans, however, over the lifespan of the fan you recoup this costs and then some.  Use an energy calculator to compare fans using their listed wattage against your local electrical rates.  AC fans can often cost hundreds of dollars or more over the lifespan of the fan (use eight years as an average fan lifespan for Fantech or RadonAway pro-grade fans).

For the most energy-efficient radon system possible: use a radon professional that specializes in PFE testing, proper system design, and sealing; and also uses Fantech’s EC fans.  Be sure to sign up for a professional maintenance plan or follow my guide to maintaining your system to keep it running efficiently for decades.

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What do I need to know about Colorado’s new radon laws?

Colorado is one of only three zone 1, high-risk states in the US.  Legislators have seen the data and decided to pass consumer protection and awareness laws.  These laws have no mandates for homeowners, but they do raise awareness of this Class A carcinogen.  If your dwelling touches the soil anywhere in the US, please follow the EPA guidance and perform a laboratory test for radon every five years for the life of your home.

If you live that sweet, sweet van life; then party on!  No radon testing for you.


Is your radon pro licensed?  Check with the state by clicking HERE

Are you a contractor looking to get licensed?  We have course discounts available HERE

In May of 2023, Colorado passed SB23-206 which raises radon awareness for new home buyers and renters.  Click the link above to read more.  The new law requires landlords and home sellers to give written disclosures on the risks of radon to future occupants.  No mandates for testing or mitigation.  More information below:

Does SB23-206 require me to do a radon test?

No, there are no mandates with this law.  Like lead or asbestos, this is an awareness piece designed to educate buyers on the dangers they may face in their new home.

Does SB23-206 force a seller to pay for a radon test?

No, the sellers’ only responsibility is to follow the disclosure notices.  However, if they do not give these documents to the buyer, they can be sued and forced to pay for court costs, radon testing, and mitigation.

When does this law take effect?

Both radon laws are now in effect in the State of Colorado.  Please visit DORA’s webpage or call DORA for more information.


HB21-1195 information below.

In July of 2021, Governor Polis signed HB21-1195 into law*, making Colorado one of only a few “licensed” states. The law is regulated by DORA: the department of regulatory agencies for the state of Colorado. These Colorado radon regulations are part of a sunset law, so it will be in place for ten years. If the citizens demand it’s kept, it will have to be voted into law again in 2031. If its deemed superfluous, it will expire in ten years.

How does the new radon law affect Coloradans?

Colorado’s new radon law is a consumer protection law. Stakeholders in Colorado, including myself, have seen an unprecedented number of consumers with “bad mitigation systems” or having professional radon tests being performed with substandard procedures and equipment.  These systems do not meet industry best practices and put the homeowner in significant danger. Imagine you bought a furnace and it was installed by someone with no training or experience. That furnace could break, maim, or even kill you. That’s why HVAC professionals are licensed. We see the same need for radon professionals.

Radon is a class A carcinogen. It is estimated that nearly two Coloradans die every day as a result of prolonged radon exposure. Radon in Colorado is a serious matter and Colorado Radon professionals have fought to treat it as such. We want to see homeowners safe, and in order to do that we need to penalize contractors acting in bad faith. When a homeowner buys a radon system, it should work. Our hope is that this new Colorado radon law will curb the installation of bad systems and prevent needless disease in our fellow citizens.

What do contractors need to know?

  1. Take and pass an NRPP* accredited course (*National Radon Proficiency Program)
  2. Pass your exam, obtain your national credentials
  3. Register your credentials with DORA
  4. Follow industry code, which includes being licensed and bonded

If you take the reasonable four steps above, you’ll be in the clear. Accredited courses are inexpensive, ranging from $500-2,000, and can often be completed in a few days in person or a few weeks online.

What happens if I don’t get licensed?

Unlicensed radon mitigation and testing contractors open themselves up to criminal liability under Colorado’s radon laws and regulations. Fines and misdemeanor criminal charges can be brought against them immediately. There is no grace period for this act. Licensing starts July 1st, 2022.

How will someone know I’m not following protocol?

Unlicensed or bad work can be reported by anyone. This means anyone can report their competition.

For more information, visit DORA’s radon site, or call RMAARST 720-629-9819

As an industry stakeholder, I’m proud of the steps we’ve taken and happy the State legislature of Colorado agrees with our assessment that we need help. Homeowners still must be savvy consumers and check the credentials of any contractor performing work on their home. However, our hope is that soon enough, contractors wouldn’t dream of going to work without training. Licensed pros are proud of their work. See for more information on how to choose a radon mitigation or testing contractor, and keep up with radon news and safety tips on our blog.

*This page is intended for general informational purposes only and is not intended as specific or legal advice relating to bill SB-23-206, HB 21-1195, or any other statutes, regulations, or ordinances.  Please consult your legal counsel and the State of Colorado to ensure that you are operating within the parameters of the law.  PDS Radon Supply is not responsible for your actions.